Fabrication and characterization of a micromechanical sensor for differential detection of nanoscale motions

• Published in: Journal of microelectromechanical systems Vol. 11; no. 6; pp. 703 - 708
• Main Authors: Savran, C.A., Sparks, A.W., Sihler, J., Jian Li, Wan-Chen Wu, Berlin, D.E., Burg, T.P., Fritz, J., Schmidt, M.A., Manalis, S.R.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.12.2002; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Biological; Biological and medical sciences; Biosensors; Biotechnology; Chemical and biological sensors; Deflection; Devices; Exact sciences and technology; Fabrication; Frequency; Frequency ranges; Fundamental and applied biological sciences. Psychology; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical instruments, equipment and techniques; Mechanical sensors; Methods. Procedures. Technologies; Micromechanical devices; Micromechanical devices and systems; Motion detection; Nanobioscience; Nanomaterials; Nanostructure; Noise level; Noise levels; Physics; Sensor phenomena and characterization; Sensors; Various methods and equipments; Design; Optical measurement; Atomic force microscopy; Interdigital transducers; Micromechanical resonators; Functionalization; DNA; Displacement measurement; Biosensors; Microdisplacement; Microsensors; Production process
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2002.805057

We have micromachined a mechanical sensor that uses interferometry to detect the differential and absolute deflections of two adjacent cantilevers. The overall geometry of the device allows simple fluidic delivery to each cantilever to immobilize molecules for biological and chemical detection. We show that differential sensing is 50 times less affected by ambient temperature changes than the absolute, thus enabling a more reliable differentiation between specific cantilever bending and background effects. We describe the fabrication process and show results related to the dynamic characterization of the device as a differential sensor. The root-mean-squared (r.m.s.) sensor noise in water and air is /spl sim/1 nm over the frequency range of 0.4-40 Hz. We also find that in air, the deflection resolution is limited only by the cantilever's thermomechanical noise level of 0.008 /spl Aring//Hz/sup 1/2/ over the frequency range of 40-1000 Hz.